Yi Woo was a Shou healer who operated a clinic in the Xiousing district of Marsember. In his youth, he studied the arcane as well as the martial arts. Later in life he moved to Xiousing and opened a healing clinic that served both Shou and native Marsembens. He would heal anyone regardless of their ability to pay. Woo became frustrated with the Purple Dragons' inability to fight crime so he became a secret vigilante, operating under the cover of darkness.